Extract the pure per-provider chat-URL normalizers (normalizeBailianMessagesUrl,
normalizeDataRobotChatUrl, normalizeAzureAiChatUrl, normalizeWatsonxChatUrl,
normalizeOciChatUrl, normalizeSapChatUrl, normalizeXiaomiMimoChatUrl,
normalizeOpenAIChatUrl, getOpenRouterConnectionPreset) verbatim into the leaf
default/urlNormalizers.ts. Host imports them back into buildUrl/transformRequest; the
now-dead build*ChatUrl/normalizeBaseUrl imports move to the leaf. All module-private
(no re-export).
Host 864 -> 815 LOC (shrunk below its frozen baseline). Byte-identical bodies (verbatim
45/45), leaf does not import the host (no cycle). buildHeaders/execute/auth untouched.
Adds a split-guard; consumer tests stay green (executor-default-base 49,
anthropic-compatible-bearer 3, strip-client-metadata 3).
